1. Field of the Invention
The invention concerns an electrical conductor cable for transmitting information. It also concerns a method of manufacturing a cable of this kind.
2. Description of the Prior Art
Nowadays information is transmitted via electrical cables comprising a large number of conductors and at very high frequencies. The increased frequencies and the increased number of streams of information to be transmitted in parallel on separate conductors leads to the necessity of providing effective insulation between the various electrical conductors assembled together in the same cable. The risk of crosstalk increases with the number of conductors and the frequency. Crosstalk is the result of information transmitted on one conductor being radiated toward another conductor.
The information is usually transmitted by pairs of conductors and the pairs are insulated and/or shielded from each other to prevent crosstalk, or near-end crosstalk.
The most usual solution to the problem of shielding each pair of conductors is to wrap a metal or metalized tape around each pair in a helix, the cable being formed by assembling the shielded pairs into a common protective sheath. Shielding the pairs individually is slow and difficult. To connect the resulting cable the individual shields of the pairs must be removed to obtain access to the conductors, which makes the connection operation, which is usually carried out on site, difficult.
To overcome these drawbacks, document FR-2 738 947 proposes a cable in which the electrical shields of the various conductors, in particular the pairs, comprise a central member with radial fins separating the pairs from each other and partially shielding each pair and a peripheral shield around the central member and the pairs, the peripheral shield completing the shielding of each pair. However, the fins of the central member form stiffener ribs and a cable made this way is unsuitable for many applications in which the cable needs to be flexible. Also, a cable equipped with a central member of the above kind is not easy to manufacture as it necessitates an extrusion operation.
The invention provides a flexible cable having good insulation between conductors, pairs or quads and which is also particularly simple to manufacture and use.